The performance of Proton exchange membrane fuel cell (PEMFC) has been experimentally investigated. An experimental set-up was designed to study the effects of operating parameters such as cell temperature, gas humidification, and cell operating pressure on the performance of fuel cell. The results indicated that the output power increase with the increase of humidification ratio. Furthermore, an increase of cell pressure results in a significant increase of cell power. The results indicated that increasing of the temperature leads to a decrease of cell power. The results are explained and discussed in more details for different operational parameters.

Fuel cells based on polymer electrolyte membranes (PEMs) are attractive power sources because they are efficient, non-polluting, and do not rely on non-renewable fossil fuels. Water management is a critical design issue for these fuel cells because the PEM must be maintained at the proper water content to remain ionically conducting without flooding the electrodes. Furthermore, portable PEM power systems should operate at water balance. That is, water losses from the cell should be balanced by the rate of water production from the fuel cell reaction. A portable system that operates at water balance does not require an external supply of water. The rate of water production depends on the cell’s electrochemical characteristics. The rate of water loss depends on the flow rates of reactants and products, transport of water and fuel across the PEM, and the stack operating temperature. This paper presents the basic design relationships that govern water balance in a PEM fuel cell. Specific calculations are presented based on data from hydrogen/air and direct methanol fuel cells currently under development for portable power systems. We will show how the water balance operating point depends on the cell operating parameters and show the sensitivity to off-design conditions.

It is common in a PEM fuel cell to have the air flow through serpentine channels with a rectangular cross-sectional shape in a flow plate. There is a porous diffusion layer adjacent to this flow plate. Flow cross-over of air through the porous diffusion layer from one part of the channel to another can occur, as a result of the pressure differences between different parts of the channel, and it causes the flow rate through the channel to vary with distance along the channel and also has an influence on the pressure distribution along the channel. These changes in the pressure distribution as a result of cross-over can effect the fuel cell performance. In the present study the conditions under which cross-over occurs and the effects of the cross-over on the pressure distribution and local channel flow rates have been examined by numerically solving for the flow through the plate-porous layer assembly. Two flow channel arrangements have been considered: (i) a single serpentine channel flow system with different land widths between the channel sections (ii) a two-channel parallel serpentine flow system. A single phase flow has been considered. The governing equations have been written in dimensionless form using the channel width as the length scale and the mean velocity in the channel as the velocity scale. The resultant set of dimensionless equations has been numerically solved using a commercial finite element code, FIDAP. The solution was obtained by simultaneously numerically solving the dimensionless governing equations for the flow in the channels and for the flow through the porous gas diffusion layer. The numerical calculations were obtained using a commercial finite element code, FIDAP.

Recent advances in PEM fuel cell systems have demonstrated their role in the production of clean and efficient power. However, due to complexities and safety concerns in the storage and transport of hydrogen, development of on-board fuel processing of hydrocarbon into hydrogen is being considered a critical issue in the success of the fuel cell technology in transportation application. In this paper, a novel concept of scalable silicon micro-reactor with an integrated platinum heater is developed for preferential CO oxidation. The performance of the micro-reactor is assessed and compared to a packed-bed reactor model. Complementary experimental and modeling efforts are made to identify the optimal thermal design parameters. It is demonstrated that the silicon micro-reactors successfully achieves the objectives of scalability without suffering from loss of efficiency due to the mass transfer limitations.